The practice of using
tactical aircraft to carry high power radar jamming equipment
originated
during WW II, when RAF Defiants fitted with Mandrel jammers first
disrupted the operation of the Luftwaffe's Freya A-band acquisition
radars.

Defiants equipped with Mandrel jammers or Moonshine deception
repeaters and rocket firing Typhoons thus laid the foundations of
modern
tactical support jamming and defence suppression. The use of these
types
also underscores a trend followed well into the seventies; that of
fitting offensive electronic warfare equipment and defence suppression
weapons to types which had outlived their usefulness in their
originally envisaged roles. It wasn't until the late 1960s that the
pivotal role of Electronic Warfare (EW) in tactical defence penetration
and suppression was fully accepted and as a result, specialised
derivatives of frontline tactical aircraft developed to fill these
roles.

The first of these to fill the former role were the US Navy's
EA-6A and EA-6B derivatives of the A-6 Intruder family, two types which
supplemented and supplanted the ungainly and obsolete EF-10s and
EKA-3s.
These new aircraft were true Support Jamming (SJ) aircraft, capable of
flying Escort Jamming (EJ) and Stand-Off Jamming (SCJ) missions.
Standoff jammers will orbit outside of the lethal radius of hostile
defenses and jam radar and communications from a distance, escort
jammers accompany strike aircraft into hostile airspace and jam
acquisition radars and communications from close range.

The proliferation of radar guided Surface to Air Missiles
(SAM) and radar directed guns (AAA) in the 1960s coupled with the
increasing payload/radius performance of tactical aircraft created a
situation where tactical fighter-bombers were up against air defenses
built to stop strategic bombers fitted with extensive radar and
communications jamming equipment. In this situation tactical aircraft
are at a disadvantage - while the use of their onboard radar warning
receivers (RWR or RHAW) and defensive jammers (ECM) can defeat
individual hostile weapons, the defending side has the advantage of
seeing the big picture and thus concentrating its SAM, AAA and fighter
resources to maximum effect.

Firing multiple SAMs at a single aircraft can and often will
saturate the crew and jammers' workload thus increasing the likelihood
of a kill. This advantage is most easily destroyed by high power
jamming
of the defending side's acquisition and Ground Control Intercept (GCI)
radars and associated communications network. This capability is
available in large strategic bombers which can carry a dedicated
Electronic Warfare Officer/Defensive Systems Operator and thousands of
pounds of powerful jamming equipment in addition to the aircraft's
(self) defensive RWR/RHAW and ECM. Fitting high power jammers and
associated management systems to every tactical aircraft is however
physically impossible given equipment size/ weight alone and thus the
only realistic solution is to dedicate some tactical aircraft to the
carriage of ordnance and some to the carriage of jamming equipment.

A Tactical Jammer (Tacjammer) is thus a high performance
tactical aircraft equipped as a Support Jammer and typically tasked
with
penetrating a tactical air defence system to disrupt it at close range
with high power jamming of its surveillance, acquisition and GCI radars
and communications network.

Understandably any Support Jammer is a lucrative target
fitted
with expensive equipment and carrying expensive to train operators,
therefore a Tacjammer must have an ability to evade SAMs and fighters
at
least as good as but preferably better than the regular version of the
same aircraft. Furthermore, a Tacjammer is penalised in radius
performance as unlike strike aircraft it cannot shed 4,000 to 12,000 Ib
of weight (ordnance) over the target if the going gets tough.

In practice Tacjammers are implemented as derivatives of
tactical strike aircraft with airframe modifications as required to
accommodate internal and external elements of a Tactical Jamming System
(TJS) and fitted with enhanced derivatives of the defensive ECM carried
by the core aircraft. This philosophy is evident in established types
such as the EA-6B Prowler and EF-111A Raven and in newer types such as
the NATO Tornado ECR (Electronic Combat/Recce) and presumably the
Russian Fencer E(ECM) subtype.

The Grumman EA-6B Prowler

Colloquially known as the Queer, the EA-6 is the USN's
principal Electronic Warfare aircraft. The Prowler is essentially a
stretched A-6 airframe with additional stations for two more crew
members and various detail airframe changes to accommodate the
extensive
jamming system. First flown in May, 1968, the EA-6B first deployed in
1971 and subsequently played a major role in the Linebacker II campaign
disrupting the North Vietnamese air defence system in support of Navy
strikes and SAC B-52 raids.

The Prowler has retained much of the A-6 airframe with the
wing, centre-section, tail and mid fuselage very close to the original.
The wing was however strengthened to increase the g-limit at high gross
weight and the rear fuselage was stretched to compensate for the most
substantial structural change, the 4.5 ft stretch and reshaping of the
forward fuselage. The new forward fuselage provided space both for two
ECMOs and a substantial volume of mission specific electronic
equipment.

The other highly visible change to the airframe is the
bulbous
receiver antenna fairing at the top of the vertical stabiliser. These
airframe changes increased gross weight up to nearly 60,000 Ib which
forced the strengthening of the undercarriage and the fitting of
11,200lb P&W J52-P-408 powerplants in all but the earliest
airframes; the Prowler will reach 520kt at sea level. The EA-6B
apparently handles much like an overweight A-6 although the aircraft
has
had a high accident rate due to reduced stall margins. A programme is
under way to improve low speed handling which is particularly critical
on final approach prior to trapping on a carrier flight deck (USN
flying
technique emphasises AoA/power management on final. (The A-6/EA-6 thus
lands with airbrakes deployed to maintain the engines in a responsive
RPM range). Specific changes will include a vertical stabiliser
extension above the tail fairing. recontoured flaps and slats and
linking the wingtip air brakes into the flight controls to function as
additional ailerons at low airspeeds.

As an operational asset the eleven squadrons of USN/USMC
Prowlers have no equivalent; the EA-6Bs provide SOJ and escort jamming
support for strike aircraft while also providing electronic recce and
support jamming for the fleet if threatened by hostile strike aircraft.

The source of the Prowler's potency is the Eaton/AIL
AN/ALQ-99
Tactical Jamming System. The Basic/Excap ALQ-99 is comprised of a
Frequency Set-on Receiver set. up to five external jamming pods and a
central processor tied into an IBM AYQ-6A central computer. The ALQ-99
is integrated with a General Instrument ALR-42 System Integration
Receiver set.

Functionally the ALR-42 SIR is at the top of the chain - it
is
a sophisticated radar warning receiver which detects and prioritises
threat radars (threats) for power managed jamming by the ALQ-99 or
the
aircraft's defensive ALQ-41 trackbreaker ECM (also supported by the
APR-27 SAM launch warning receiver). Power management is a term which
refers to the allocation of available jamming power in such a way that
the greatest threats receive the most power and are thus most strongly
degraded.

Threat parameters are passed by the ALR-42 SIR to the ALQ-99
which locks its set-on receivers on to the designated threats. Unlike
conventional RWRs, the set-on receivers can actually remember and
analyse the threat signal waveform (employing a Frequency Memory Device
and Signal Processor) and provide parameters used by the ALQ-99 central
processor to programme the allocated jammer. The ALQ-99's jammers are
carried in external 950lb pods each of which carries typically two 2 kW
transmitters, a control computer tied to the computer in the parent
aircraft and a substantial volume of dedicated electronics (power
supplies, exciters, drivers) to support the transmitters. Transmitter
power is provided by a ram air generator at the front of the pod with
transmitter antennas under the forward ventral pod radome.

The ALQ-99 offers several noise/spot-noise jamming modes
(refer TE Sept 88) and may have other capabilities such as false target
generation - no doubt a well kept secret. In terms of management, the
ALQ-99 can be operated in three primary modes. Automatic, where the SIR
detects threats, the computer sorts them and the jammers jam them.
Semiautomatic, where the operator selects and controls the jammers; and
Manual, where the operators also identify and prioritise threats.

The ALR-42/ALQ-99 provides the ability to jam high power
surveillance, acquisition and tracking radars; this capability is
supplemented by a Sanders ALQ-92 Communications Jamming System which
disrupts GCI communications links, this device was also earlier carried
by EKA-3B standoff jammers.

This suite was used in early Basic revision J52-P-8 powered
EA-6Bs which provided three band coverage (C,D,E ?), these were after
1973 rapidly supplemented by Excap aircraft with six band (C to H ?)
coverage and J52-P-408 powerplants. From 1976 EA-6Bs were delivered to
Icap standard fitted with faster computers, new cockpit display sets,
upgraded comm/nav/IFF, Automatic Carrier Landing System and the
standard
USN ALQ-126A trackbreaker defensive ECM. The EA-6B Icap was supplanted
by the current Icap 2 version the prototype of which first flew in
1980.
The Icap 2 upgrade saw substantial electronic improvements to the
jammer hardware with the ALQ-99 providing full eight band (C to J)
coverage.

The Icap 2 Prowler carries a USN standard CDC AYK-14 Tactical
Computer tied into a MIL-STD-1553B databus. and revised operator
display
sets. Functionally the AYK-14 performs a similar management function to
that of the AYK-14s in the F-18, driving the pilot's digital flight
instrument displays. In the Prowler however it also ties into the
ALQ-99
TJS, an onboard Recorder/ Reproducer and a dedicated ASN-123 Display
Computer (front end processor for the technical) which drives the
digital displays and keyboards used by ECMO's 2 and 3 in the aft
cockpit.

The use of the 1553 bus provides tremendous system level
flexibility with the AYK-14 also driving a digital display in the front
cockpit and in late Icap 2 aircraft tying into a CV3976/AWG HARM
control/armament panel. The AGM-88 High-speed Anti Radiation Missile
(HARM) was a late addition to the EA-6B having been implemented in a
crash 18 month programme with first production deliveries this year.
The
absence of HARM was long criticised by Prowler crews who are generally
considered to be the source of most electronic warfare and defence
suppression expertise in carrier airwings, usually planning the HARM
strikes flown by the A-7E and F-18A/C squadrons.

Integrating the HARM with the ALQ-99 software and the large
shipboard TSQ-142 TEAMS (Tactical EA-6B Mission Support) mission
planning computer mission parameters into the ALQ-99 before launch via
a
magnetic tape cassette. In practice this means that Prowler missions
can
be preprogrammed in detail using the TEAMS to concentrate available
intelligence thus significantly speeding up preflight preparations. The
addition of HARM provides the Prowler with the teeth it needs to bite
particularly problematic threat radars while also demonstrating an
emergent trend to merge the tactical jamming and defence suppression
roles, of the Tornado ECR.

The EA-6B Advcap upgrade is currently in the pipeline and
will
include new high performance Litton receiver-processors which should
enhance the ALQ-99's capability as a deception jammer. Included is a
new
Eaton/AIL exciter-modulator for the high band transmitters providing
more diverse and sophisticated jamming modes. Two additional wing
pylons
and 12,000 Ib J52-P-409 engines will allow a full complement of jammer
pods plus two HARM rounds. A new pod mounted ITT ALQ-149 Communications
Jammer will also be carried.

USN/Grumman EA-6B Prowler. The EA-6B is the US
Navy's
principal electronic warfare platform. Eleven squadrons of Navy and
Marine Corps Prowlers provide standoff and escort jamming support for
Navy strike aircraft while also providing electronic recce and support
jamming for the fleet if threatened by hostile strike aircraft.
(Grumman)

The Grumman/General Dynamics
EF-111A Raven

The EF-111A is the USAF's first true tacjammer. The need for
such an aircraft became most apparent in South East Asia where the USAF
EB-66B/E was constrained to the SOJ role lacking the performance to
survive in a MiG and SAM saturated environment. While the USAF
recognised the effectiveness of the Navy EA-6B, the EA-6B lacked the
performance and endurance required by the USAF to support its fast
F-111
and F-4 tactical fighters. The high density European theatre would
require an upgraded ALQ-99 and a high performance airframe to carry it.
The analogue F-111A was the natural choice with some airframes surplus
to the A-model wing. Both prototypes of the EF-111A flew in early 1977
and were rebuilt from existing low time airframes, with 42 production
rebuilds being delivered from 1981 onward.

The airframe of the EF-111A differs little from the basic
F-111 A the only major structural changes being the fitting of a large
fairing to the top of the vertical stabiliser and the installation of a
jammer pallet in the internal fuselage weapon bay. Internal changes
were
substantial with a resculptured cockpit, numerous antenna and wiring
installations and presumably a major increase in electrical power
generation capability to support the thirsty jammer electronics. The
aircraft retained the geriatric AJQ-20A nav-attack and APQ-110 Terrain
Following Radar (TFR) but acquired a newer APQ-160 attack radar.

The EF-111A carries the ALQ-99F which had 70% commonality
with
the Navy ALQ-99. The ALQ-99E offered much faster threat acquisition and
identification while being substantially automated with only one
Electronic Warfare Officer required to operate it. Each jammer in the
99E could cover a larger number of threats than the Navy version (spot
noise jamming where the jammer dwells on the frequency of each threat
radar for a programmed fraction of a second after which it retunes to
the next and so on ...) and used multi-mode antennas which allowed
omnidirectional and directional transmission. Ten jammers each with a
steerable antenna are carried in the weapon bay, the antennas
protruding
below the fuselage concealed under a distinctive canoe radome. The USAF
are understandably secretive about the 99E therefore little has been
published on the system level tie-in with the remaining aircraft
systems.

The aircraft also carries the upgraded ALR-62(V)4 Terminal
Threat Warning System (TTWS) which is designed to look through the
powerful jamming transmissions of the ALQ-99E. Defensive jamming is
provided by the capable ALQ-137 trackbreaker ECM which is common to
SAC's FB-111As (refer TE Sept 88) and provides fore and aft coverage.
Antenna placement on the EF-111A differs from the F-111 with receiving
elements of the ALR-62, ALQ-137 and ALQ-99E situated in the tail
fairing
with some ALQ-137 transmit antennas and ALR-62 forward antennas on the
wing gloves and nose.

Given the architecture of the EA-6B/ALQ-99 and the known
major
modifications to the ALR-62(V)4, it is very likely that the ALR-62 TTWS
performs a similar function to the ALR-42 SIR in the EA-6B, detecting,
classifying and prioritising threats for the automatic set-on receivers
of the ALQ-99E and defensive ALQ-137. Under the control of the
ALQ-99E's
internal processor jammers would then be directed against selected
threats. Cockpit interior layouts released by the USAF indicate a large
rectangular CRT display on the right hand side of the EWO's panel
beneath which is a control keyboard and above which is a combined
TTW/DECM indicator panel. A bar telltale status indicator is provided
for the ten jammers which have individual mode controls and automatic
and manual steering controls on a right hand side console panel.
Available information suggests coverage in six bands in early aircraft,
it is likely that subsequent upgrades provide full C to J band coverage
as in the Navy Icap Prowler.

USAF/Grumman/General
Dynamics EF-111A Raven. USAF EF-111As
play a major
role in the European theatre, concealing AWACS airborne command posts
and other high value assets from Warpac long range SAMs and fighters.
Other missions include standoff jamming support for close air support
missions and escort jamming support for deep penetration strikes. The
effectiveness of the EF-111A in the latter role was amply demonstrated
by the stunning TAC raid on Tripoli in 1986, supported by three Ravens
from the 42nd Electronic Combat Squadron at upper Heyford in the UK.
(US
Air Force).

EF-111A ALQ-99 transmitter
installation (above, below). Transmitter modules, largely
identical to the naval variant, were installed on a pallete
mounted in the weapon bay. The canoe radome covered
the steerable antennas. Arbitrary module mixes could be fitted on the
flightline, for a total of up to ten (US Air Force).

At the time of writing the US$81.5m Eaton/AIL/General
Dynamics
upgrade programme, running since 1984, was cancelled by USAF Systems
Command who regarded cost overruns and schedule slippages in the
contract as unacceptable. This upgrade involved new high band exciters
for the ALQ-99E jammers many of which were originally designed by AIL;
of the 49 Line Replaceable Units in the ALQ-99E, a third were designed
and built by AIL. The USAF was to decide whether completion of the
programme is to be awarded to Grumman who lost out in the 1984 bidding.
It is however certain that the cost overruns and delays will postpone
the USAF's plan to fit the upgraded Litton receiver set developed for
the EA-6B Advcap thus leaving the EF-111A's capabilities well behind
those of its Navy counterpart.

It is unclear what impact this will have on longer term plans
which apparently include phased array antennas (much like the B-1
B/ALQ-161) for the jammer transmitters; these will allow time sharing
an
antenna between several threats without a penalty in power delivered to
the threat. Phased arrays allow nearly instantaneous pointing of very
tight beams which concentrate more jamming power on the threat. It is
almost certain that the EF-111A will undergo the full USAF F-111 A/E
offensive avionics/ flight controls upgrade currently under way and
proposed for RAAF F-111 s.

The longer term outlook is most likely that of the EA-6B and
EF-111A being replaced by a derivative of the A-12 Advanced Tactical
Aircraft (ATA) early in the next century. The ATA is currently being
designed as a stealthy multi-role replacement for the A-6E and later
F/FB-111 aircraft.

Mission Profile

The EA-6B and EF-111A have been optimised for the naval
strike
and high density air/land battles respectively, therefore a broad
spectrum of missions is flown.

The EA-6B will spend most of its time in two roles -
electronic support of the fleet and support jamming during air strikes.
The former role involves a considerable amount of electronic recce
(ELINT) in conjunction with dedicated EA-3B, EKA-3B, ES-3A and ASW/ASuW
S-3A/B aircraft, sniffing for and investigating the electromagnetic
emissions of hostile naval forces and shore based installations.

The other aspect of this role is the jamming of radars on
hostile surface vessels, recce and strike aircraft in support of
antishipping strikes by friendly aircraft or maritime air superiority/
defence missions directed at hostile maritime strike aircraft. In this
uniquely naval mission the EA-6B is a potent offensive and defensive
tool. The other major aspect of the Prowler's mission is support
jamming
and defence suppression during strikes on coastal targets. These
missions may involve penetration with escort jamming or simply
stand-off
jamming.

USN/Douglas EKA-3B
Skywarrior.
The elderly EKA-3Bs and EA-3Bs provided support jamming and electronic
recce during the Vietnam conflict. In the latter role the aircraft is
still used although it is to be replaced by ES-3A Vikings rebuilt from
ASW airframes (US Navy image).

The EF-111A has been by design targeted at the high density
central
European air/land battle and three classes of mission are envisaged.

In Stand-Off Jamming missions, the EF-111As would operate at
altitude 200 to 400 nm from the battle front from where they would
snow Warpac long-range surveillance radars probing for Allied AWACS,
JSTARS, TR-1 surveillance/recce aircraft, EC-130H Compass Call
communications jammers and tankers. These valuable but slow moving
aircraft are vulnerable to long range SAMs such as the SA-5 (range cca
160 nm) recently deployed in central Europe, while it also appears that
the Flanker and new AS-11 ARM firing defence suppression Foxbat F would
be employed to dash through the NATO fighter/SAM screen on dedicated
AWACS killing sorties.

Operating in pairs the EF-111As would blind surveillance
radars and attempt to confuse ground based direction finding systems
thus preventing the Warpac from locating and destroying some very
important assets.

In Close-in Jam missions the EF-111A would approach the
forward battle area and blind the Long Track, Flat Face, Clam Shell and
Land Roll mobile surveillance/acquisition radars to approaching NATO
A-10, Jaguar and Harrier Close Air Support (CAS) aircraft. This leaves
the CAS aircraft only up against the Warpac's terminal defences and
allows ingress well above 500 ft while over friendly airspace thus
saving a considerable amount of precious fuel.

On Primary Jamming missions, the EF-111As fly as escort
jammers with deep penetration strike aircraft such as the F-111 E/F.
Typically the aircraft all penetrate using TFR at very low level and
hopefully undetected. As the strike aircraft approach the radar horizon
of the target's area defences, the EF-111A would pop up to several
thousand feet and jam any radars which would be considered a threat,
while the strike aircraft pound the target from tree top altitude.
These
tactics were employed against the Libyans in 1986 quite successfully
with no SAM hits reported.

High performance tactical jamming aircraft are a necessary
part of any major air power and represent the most effective means of
disrupting the control of the enemy's defensive system. Once that has
occurred the individual SAM and AAA systems have no means of
coordinating and concentrating their fire on specific targets. This
renders them essentially ineffective when confronted by the onboard
defensive jammers of the attacking strike aircraft.

While the acquisition of specialised aircraft such as the
EA-6B and EF-111A is out of the reach of smaller air forces, multi-role
tactical jamming/defence suppression aircraft such as the Tornado ECR
are an affordable and reasonable means of performing these roles. It
will be interesting to see whether the RAAF responds to this emerging
trend. The payoff is considerable.

[Editor's Note 2005: Despite
this
early
1989 analysis and a generous offer by the US Air Force
during the late 1990s, the Australian DoD has never displayed any
interest in acquiring any Electronic Combat/Attack capabilities.]

The
EA-18G 'Growler' is expected
to replace the EA-6B on CVBG flight decks. It is built around the
ALQ-99 system (Boeing image).